1. Field of the Invention
The present invention relates to telecommunication technology and, more particularly, the invention is directed to optimization of the route of a telecommunication connection that is set up in a mobile communication network.
2. Description of Related Art
For a teleoperator, i.e. an owner or operator of a telecommunications network, it is important that telecommunication connections be set up in an optimal manner. Optimization may for example be based on the length of the route of the connection or on the network load resulting from the connection. Because the traffic in mobile communication networks is continuously increasing, it is particularly important that the load in such networks remain as low as possible. One approach to reducing the load in a mobile communication network is to set up or establish the connection to the mobile switching center then serving the called subscriber via a route that is as short as possible.
An intelligent network is formed by switching, control and functional components and a signaling network. A service switching point (SSP) of such intelligent networks is a modified telephone exchange that analyzes the traffic passing therethrough. When the SSP detects a certain number that meets a triggering criterion, it transmits a service request to a service control point (SCP). The information required for service control is stored in a service data point (SDP), from which the service control point can obtain the information that it needs.
Service switching points are connected via signaling channels to service control points, which implement intelligent network services by utilizing a service database. A service control point may for example perform a numerical conversion from the B-number to the corresponding C-number by accessing such correspondence information from the service database.
The communication protocols used in an intelligent network are rules by which the components of the intelligent network talk to each other. These protocols defme the interfaces between components as well as the structure of the messages exchanged between them. Intelligent network components communicate with each other using common channel signaling (CCS). By ITU-T definition, common channel signaling is known as CCSS No 7. For communication between components, an intelligent network uses the services of the INAP (Intelligent Network Application Part) defined by ITU-T; the INAP application part is an intelligent network application protocol used, for example, for communication between a service control point and a service switching point. The MAP application part, on the other hand, is a portion of the signaling system of a mobile communication network that is used for signaling between the switching centers and registers of the mobile communication network.
In the GSM (Global System for Mobile communications) system, a call to be set up or established is routed as follows. A call setup request is sent from the calling subscriber's (A-subscriber's) terminal equipment to a gateway mobile switching center (GMSC), which then sends a query to the called subscriber's (B-subscriber's) home location register (HLR) to determine the mobile switching center (MSC) under which the B-subscriber's terminal device is currently located. The home location register is implemented as a database that contains such information as subscriber data, subscriber location data, call control data, short-message services and billing data.
Next, the home location register requests the visitor location register (VLR) for a roaming number MSRN (Mobile Subscriber Roaming Number) and returns the roaming number to the GMSC. The visitor location register is implemented as a database in a mobile communication network which contains the information required for the transmission of calls about each mobile subscriber currently located in the area of the network. The roaming number is a temporary identification number that is allocated to a mobile station recorded in the visitor location register and which is used by the mobile communication system for the muting of calls addressed to that particular subscriber.
Based on the roaming number, the GMSC then routes the call originated by the A-subscriber to the mobile switching center in whose location area (LA) the B-subscriber is currently located. The B-subscriber's mobile switching center in turn sets up a connection with the B-subscriber's terminal device.
The primary problem with the above-described routing procedure is that calls addressed to mobile stations are not automatically routed via the shortest route to the proper mobile switching center but may, instead, be routed via several switching centers. One solution that has been applied to eliminate this problem is to provide some service nodes (SN) and service control points with an MAP interface, thus making it possible to implement functionality and service similar to that provided by present invention. Such solutions, however, disadvantageously they bind the service to a certain base and assume that the service control point or service node is provided with an MAP interface.
In the procedure of the present invention, on the other hand, the routing of calls addressed to a terminal device is optimized by using an intelligent network service and a special gateway. By means of that gateway, a query is sent from the intelligent network system to a subscriber register to obtain B-subscriber data and, using that data, the call to be set up is routed directly to the mobile switching center in whose area the B-subscriber's terminal device is currently located. This arrangement and methodology additionally makes it possible to utilize other GSM network services.